Hot flushes pose a significant public health concern world-wide. These perimenopausal symptoms are the primary reason that women seek medical care during the menopausal transition. Hot flushes often negatively impact the quality of life of women because they are associated with sleep disturbances resulting in fatigue, depression, irritability, and forgetfulness, as well as acute physical discomfort and negative effects on work. Current therapies include estrogen or hormone (estrogens + progestins) therapies (ERT and HRT), clonidine, the selective serotonin and/or norepinephrine reuptake inhibitors, and gabapentine. Although ERT or HRT is efficacious in preventing hot flushes, a large number of women cannot or do not want to take estrogen. The efficacy of the other therapies is questionable. Therefore, there is a huge unmet need for a better and safer ERT or HRT. We propose in this application that para-quinol of 17b-estradiol (Q-E1) has the potential to be considered as the optimal ERT. We have shown earlier that para-quinol of estrone (Q-E1) functions as a pro-drug and following its absorption its is converted in selective tissues to E1 via an enzyme catalyzed mechanism involving NADP(H). This conversion is effective in the brain but not in the uterus, breast, or the pituitary gland. Therefore, treatment with quinols of estrogens do not have uterotropic (spotting, bleeding, cancer) and mammotropic (breast cancer) liabilities like any other estrogens, including the frequently used Premarin. Since E2 is the primary and most potent estrogen produced by the human ovary, we propose to consider Q-E2 as a pro-drug for the treatment of perimenopausal symptoms, primarily hot flushes. Our pilot data strongly indicate that Q-E2 blocks hot flush symptoms in a rat model of hot flush, but does not stimulate proliferation in MCF-7 breast cells or the uterus at doses that block the hot flush symptoms. Therefore, Q-E2 seems to be a novel, safe, and optimal ERT for alleviating perimenopausal hot flushes. The proposal describes a series of studies aimed at (i) dissecting out the dynamics of Q-E2/E2 conversion in brain areas involved in thermoregulation, (ii) establishing the optimal dose of Q-E2 following its subcutaneous and oral administration using two rat models of hot flush, (iii) provide evidence that the beneficial actions of Q-E2 are mediated via estrogen receptors, and (iv) confirm the lack of action in the uterus and breast, and the beneficial effects in the bone following its chronic administration to ovariectomized rats. The discovery of a novel and safe ERT would improve the quality of life of hundreds of millions of perimenopausal women world-wide and thus, would have a tremendous impact on public health. Although has not been tested experimentally, Q-E2 might be the choice of therapy of men in the andropause as well. In addition, the pro-drug approach we propose here could provide an impetus for drug discovery of other related or un-related therapies. PUBLIC HEALTH RELEVANCE: Peri-menopausal hot flushes pose a significant public health concern world-wide. Although hormone replacement therapy, alleviates hot flushes in the majority of women, a large number of peri-menopausal women cannot take or do not want to take hormones. Therefore, there is still a huge unmet need for better and safer therapies for menopausal symptoms. The proposal addresses this unmet need by investigating a potentially liability-free estrogen replacement therapy, i.e., the use of para-quinol of estrogen as a prodrug approach. The prodrug is converted to estrogen in brain but not uterus and breast, and as a result, it blunts hot flushes in an animal model of hot flush.